Final Project Evaluation
The Traffic Calming Program (TCP) undertook a Streamlined Speed Bump Project in the Fall of 1995 to address traffic problems identified by residents along SE 67th Avenue from Powell to Holgate.
The goal of the project was to enhance street safety and livability by reducing the 85th percentile speed of vehicles using SE 67th Avenue closer to the legal maximum speed limit of 25 miles per hour (mph). Speed bumps are the only device considered for streets like SE 67th Avenue, which are classified as Local Service Streets, are not transit or primary fire response routes and have vehicle volumes between 400 and 1700 vehicles per day. Speed bumps have proven to be effective tools to reduce vehicle speed without impacting access. It is not an intended goal to reduce traffic volume on low-volume Local Service Streets.
SE 67th Avenue serves a mixed single family residence and apartment neighborhood. Powell Boulevard, to the north, is a Major City Traffic street. Holgate Boulevard, at SE 67th Avenue's south end, is a Neighborhood Collector street. SE 67th Avenue has sidewalks and curbs. Part of the daily traffic on SE 67th Avenue is believed to be cut-through traffic.
All residents along SE 67th Avenue were invited to an open house November 15, 1995 to review and comment on the proposed speed bump installation. Two households were represented at the open house. Those who attended expressed approval for the proposed project. A petition was available at the open house for residents along SE 67th Avenue to sign and was circulated after the open house by a local resident. Of the 77 households along the street, 56, or 72.7%, signed the petition requesting speed bump installation.
Six 14-foot speed bumps, at 370 to 550 foot spacing, were constructed along the 0.47 mile stretch of SE 67th Avenue, Powell to Holgate, in April of 1996 by the Bureau of Maintenance.
As the graph shows, vehicle speeds, previously concentrated between 23 and 31 mph, have been shifted into the range of 20 to 25 mph. The 85th percentile vehicle speed before the project was 30.5 mph. After bump construction the average 85th percentile speed is 25.5 mph and ranges from a low of 19 mph (near the bumps) to a high of 27 mph.
Traffic volumes before bump construction measured 880-1350 vehicles per day (vpd). After bump construction volumes measured 670-990 vpd. Traffic volumes measured on side streets adjacent to SE 67th showed no significant increases from volumes measured prior to speed bump construction.
Traffic Calming on SE 67th Avenue, Powell to Holgate has successfully reduced the 85th percentile closer to the posted speed and enhanced street safety and livability.